FIG. 1A and FIG. 1B schematically illustrate the viewing angle of a conventional liquid crystal display (LCD) device. Referring to FIG. 1A, a schematic top view of the conventional LCD device is shown. The conventional LCD device 10 has a fixed orientation and thus the images are easily distorted when the viewer is located at certain angles with respect to the conventional LCD device 10. For example, when a viewer is located at the position A as shown in FIG. 1A, the images on the screen of the conventional LCD device 10 are distorted and obscured because the viewer is beyond the range of a preferable horizontal viewing angle for the conventional LCD device 10. Whereas, when the viewer is located at the position B, which is directly in front of the conventional LCD device 10, the images on the screen of the conventional LCD device 10 are viewed without distortion. Referring to FIG. 1B, a schematic side view of the conventional LCD device is shown. Likewise, the conventional LCD device 10 is placed at a fixed orientation and a certain height. For viewing images on the conventional LCD device 10 without distortion, the viewer 11 needs to stand within the range of the vertical viewing angle for the conventional LCD device 10.
If other viewing positions are required when the viewer is not directly in front of the LCD device for example, the viewer must manually rotate the LCD device in order to see images on the screen of the LCD device without distortion. In addition, the viewing position should be further fine tuned in order to precisely position the LCD device. The process of manually rotating and tuning the LCD device is not user-friendly. This drawback becomes more serious if the process of manually rotating and tuning the LCD device is frequently done. For solving the above problems, some techniques have been developed.
Please refer to FIG. 2, which is a schematic perspective view illustrating a display device described in Taiwanese Patent M307922. The display device 2 includes a base 21, a driving member 22, a screen 24 and a rotatable member 23. For rotating the screen 24 at a specified rotating angle, the viewer needs to input an instruction of setting desired rotating angle in a user operation interface of a remote controller (not shown) or the screen 24. By wirelessly or manually executing the instruction, the screen 24 issues an enable signal to the driving member 22. In response to the enable signal, a motor of the driving member 22 is driven to rotate the rotatable member 23 at the specified rotating angle. As the rotatable member 23 is rotated, the screen 24 coupled to the rotatable member 23 will be also rotated at the specified rotating angle. Since the execution of the instruction of setting the rotating angle is wirelessly controlled or manually operated, the process of rotating the screen is still not user-friendly. U.S. Pat. Nos. 5,250,888 and 6,115,025, which disclose methods of manually or wirelessly (e.g. by a remote controller) changing the rotating directions of the display device, have similar problems.
Another approach is disclosed in for example U.S. Pat. Nos. 6,311,141 and 6,931,596. FIG. 3 is a schematic perspective view illustrating a display device for automatic adjustment of the orientation of a screen. The images of a viewer's face 30 are captured by a camera 36 of the display device 32. An image recognition algorithm may be used to recognize the contours of the viewer's face 30, thereby analyzing the position coordinates (x, y, z) of the viewer with respect to the display device 32. The orientation of the screen 34 is adjusted according to the position of the viewer. Since this display device uses the camera 36 to capture images and the means of analyzing images needs many procedures and complicated computations, corresponding hardware components used in these literatures are not cost-effective.
Therefore, there is a need of providing an improved device and a method to obviate the drawbacks encountered from the prior art.